I finally ended up using libxml2. It does exactly what I wanted.
Here is an example.

Qt Code: 
  1. QStringList Core::queryHTML(const QString &html, const QString &query) {
  3.  
  4.     htmlParserCtxtPtr ctxt = htmlNewParserCtxt();
  5.     htmlDocPtr htmlDoc = htmlCtxtReadMemory(ctxt, html.toUtf8().constData(), strlen(html.toUtf8().constData())
  6.                                             , "", NULL, 0);
  7.  
  8.     xmlXPathContextPtr context = xmlXPathNewContext ( htmlDoc );
  9.     xmlXPathObjectPtr result = xmlXPathEvalExpression ((xmlChar*) query.toUtf8().constData(), context);
  10.     xmlXPathFreeContext (context);
  11.     if (result == NULL) {
  12.         qDebug()<<"Invalid XQuery ?";
  13.     }
  14.     else {
  15.         xmlNodeSetPtr nodeSet = result->nodesetval;
  16.         if ( !xmlXPathNodeSetIsEmpty ( nodeSet ) ) {
  17.             for (int i = 0; i < nodeSet->nodeNr; i++ ) {
  18.                 xmlNodePtr  nodePtr;
  19.                 nodePtr = nodeSet->nodeTab[i];
  20.                 QString xml = QString::fromUtf8((char*)nodePtr->children->content);
  21.                 list.append(decodeXml(xml));
  22.             }
  23.         }
  24.  
  25.         xmlXPathFreeObject (result);
  26.     }
  27.  
  28.     return list;
  29. }
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